Most vehicle differentials have a torque path from the ring gear to the differential case to the spider shaft to the bevel gear differential side pinions. Every time torque is transferred from one of these structures to another, a robust joint is required, materials of high strength must be used and the adjacent structures must be machined to close tolerances to function properly.
Typical wheel differential side pinions are driven by a spider shaft, or differential pin, that requires a through bore in each side pinion. The bore creates a thin section of material at the side pinion toe end that is a potential failure mode and which limits the maximum spider shaft diameter. Further, the spider shafts are separate pieces that can be expensive to manufacture.
Sometimes the prior art differential cases are constructed out of a relatively soft material. In these cases, differential pinion thrust washers must be located between the differential case and the side pinions to prevent excessive wear and potential failure of the case or the pinions or both.
In view of the shortcomings of the prior art differentials, it would be advantageous for a differential to have as direct as possible torque path from the ring gear to the wheel differential side pinions to reduce joint and structure loads that require expensive materials or methods of manufacture. It would also be advantageous to avoid thinning the wheel differential side pinions to reduce or prevent potential failures in this area. It would also be advantageous to eliminate the need for a spider pin to reduce materials and production costs. It would also be advantageous to eliminate the need for differential pinion thrust washers.